This application claims the priority of German Patent Application, Serial No. 101 51 234.1, filed Oct. 17, 2001, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.
The present invention relates, in general, to a revolution counter for determining the number of revolutions of rotary element rotation about a rotation axis.
European Pat. No. EP 0 658 745 B1 describes a revolution counter for counting the revolutions of a rotary element, including a sensor arrangement and a power generation system which cooperate in a way that energy pulses are delivered to the sensor arrangement also in situations when the rotary element rotates at a low speed and the regular power supply is switched off. As an energy pulse is delivered, the sensor arrangement detects at least one respective raw signal, whereby the power generation system and the rotary element are coupled in a way as to allow a determination of the angular range by which the rotary element is rotated and to infer from the detection of angular ranges the number of revolutions. A similar revolution counter is disclosed in German Pat. No. DE 44 07 474 C2.
German Pat. Publication No. DE 32 47 174 A1 describes a revolution counter with a sensor for scanning the position of a rotary element and an evaluation circuit arranged in succession to the sensor. This reference purports to ascertain one of three angular range areas on the basis of a raw signal from the sensor for each rotary position of the rotary element. Each angular range area includes hereby a plurality of angular ranges which interrelate but are separate from one another. The sensor is supplied continuously with electric energy. The evaluation circuit determines on the basis of the continuously detected raw signals the number of revolutions.
German Pat. Publication No. DE 26 39 047 A1 discloses a tachometer for measuring rotation speeds, including a sensor for scanning a rotary element and an evaluation circuit placed in succession of the sensor. The tachometer includes a power generation system which supplies the sensor with power so long as the rotary movement of the rotary element is above a minimum rotation speed.
Common to all these conventional revolution counters is the fact that the power generation system is identical with the sensor arrangement and is activated when the rotary element assumes a predetermined position relative to the sensor arrangement. A determination of the rotary position between these positions is not possible. This applies even when the sensor arrangement is supplied permanently with electric energy. Moreover, the raw signals are generated only momentarily in all these conventional revolution counters. Thus, the conventional revolution counters are constructed for determination of predetermined positions only. Whether the rotary element remains then in this rotary position or continues to move cannot be ascertained.
The prior art revolution counters suffer more shortcomings. A main drawback is the fact that only changes of the rotary position can be determined but not the rotary position per se. In addition, faster rotary movements require the provision of a different evaluation process because the power generation system, which is identical with the sensor arrangement, will no longer operate reliably when faster rotary movement are involved. Also, either the rotation direction can be determined only by a complicated evaluation of the chronological sequence of the raw signals generated when the rotary element reaches one of the predetermined positions, or a complex system is required with questionable reliability during continuous operation.
It would therefore be desirable and advantageous to provide an improved revolution counter, which obviates prior art shortcomings and is simple in structure to enable determination of the rotary position and rotation direction of a rotary element, while yet being reliable in operation.
According to one aspect of the present invention, a revolution counter for determining a number of revolutions of a rotary element, includes a sensor arrangement having a single sensor, and an evaluation circuit placed downstream of the sensor, with the sensor scanning the rotary element and generating a raw signal commensurate with a rotary position of the rotary element for ascertaining one of at least three areas of angular ranges, wherein a first area and a second area of the at least three areas of angular ranges each include a single continuous angular range and a third area of the at least three areas of angular ranges includes at least two angular ranges which interrelate but are separated from one another, and a power generation system constructed to deliver energy pulses to the sensor arrangement, when the rotary element rotates below a minimum rotation speed, wherein the sensor arrangement generates the raw signal commensurate with a determination of the corresponding one of the areas of angular ranges, wherein the power generation system and the rotary element are so coupled to one another as to ascertain for at least part of the first, second and third areas of angular ranges as determined during output of the energy pulses, by which one of the angular ranges the rotary element is rotated, and to establish the number of revolutions based on the ascertained angular ranges.
According to another feature of the present invention, the power generation system and the rotary element can be so coupled to one another as to output the energy pulses, when the rotary element rotates below the minimum rotation speed, while the rotary element is positioned in one of a plurality of known pulse angular ranges, and to ascertain on the basis of the known pulse angular ranges by which of the two angular ranges of the third area the rotary element is rotated.
As an alternative, it is also possible to determine each of the angular ranges of the third area on the basis of previously or subsequently ascertained first and second areas of angular ranges.
According to another feature of the present invention, the power generation system is able to supply energy continuously to the sensor arrangement, when the rotary element rotates above a minimum rotation speed, whereby the sensor arrangement continuously registers the raw signals and the corresponding first, second and third areas of angular ranges as well as ascertains for the third area by which of the two angular ranges of the third area the rotary element is rotated, to thereby determine the number of revolutions. In this way, a revolution counter according to the present invention, is able to correctly acquire the number of revolution for each and every rotation speed, i.e. especially for a rotation speed above the minimum level, without a need for an external power supply.
The determination of the angular ranges can be realized in a particularly simple manner, when a part of the first, second or third areas of angular ranges, corresponding to a raw signal, includes a single angular range.
According to another feature of the present invention, the sensor arrangement may be constructed for clocked operation to realize an energy-saving operation.
According to another aspect of the present invention, a method for determining a number of revolutions of a rotary element, includes the steps of subdividing a rotary element into at least a first area of singular angular range area, a second area of singular angular range, and a third area of at least two relating but separate angular ranges, scanning the rotary element, as it rotates, to generate an output signal for each rotary position, associating the output signal to a one of the angular range areas whereby the association of the output signal to the third area is realized by generating an energy pulse only when the rotary element is positioned in one of the angular ranges of the third area.